Transcript Sense of Touch

Sense of Touch
Touch and Pressure
• Often called cutaneous sensations because
most of their receptors are in the skin
• Governed by mechanoreceptors of different
types which are widely distributed
Meissner’s Corpuscles
• Primary receptors for touch are Meissner’s
corpuscles; small oval capsules of connective
tissue containing the dendrites of two or more
neurons
• If connective tissue is moved, even slightly, by
a mechanical disturbance, it contacts the
dendrites which respond by generating a
nerve impulse
Meissner’s Corpuscle
Meissner’s Corpuscles
• Most abundant in the
skin of the fingers,
palms, soles, lips, and
external genitals
• The Sensory
Homunculus represents
the density of touch
receptors in different
areas of the body
Merkel’s discs
• Merkel’s discs are another
type of touch receptor that
are found only in thin skin.
• Widespread and sensitive to
sustained pressure
• Often associated with hair
follicles
Pacinian Corpuscles
• The receptors responsible for the sensation of
pressure are known as Pacinian corpusles
• They consist of a knoblike ending of a single
sensory neuron surrounded by layers of
connective tissue that resemble the layers of
an onion
Pacinian Corpuscles
Temperature
• The sensation of temperature is detected by
free nerve endings in the skin
• These are simply the exposed ends of
dendrites and it is not well understood how
they generate nerve impulses
• Extreme temperatures will also trigger pain
receptors (below 10 and above 45 degrees
Celsius)
Pain
• Pain is a necessary evil that warns the brain
when a homeostatic imbalance needs
attention
• Pain is detected by branching dendrites of
sensory neurons that end freely throughout
the skin, muscles, and most visceral organs
• It is thought that these dendrites are sensitive
to chemicals produced as cells are damaged;
the greater the cellular damage, the greater
the sensation of pain
Pain
• Pain may also be caused by the
overstimulation of any receptor
• Visceral pain receptors tend to respond only
to widespread disturbances giving sensations
such as heartburn, intestinal cramps,
headaches, etc.
• Visceral pain is also harder to trace to its
source because major nerve pathways are
shared with other parts of the body
Referred Pain
Pain
• The intensity of pain can be controlled by use
of drugs:
• Analgesics, which interfere with the
transmission of impulses,
• Anesthetics, which produce an absence of
sensation,
• Surgery, accupuncture, hypnosis, massage,
and controlled breathing are also effective for
certain cases
Body Position
• Receptors that make you aware of body
position are known as proprioceptors
• These provide information on the degree of
muscle contraction, the amount of tension in
tendons, position of a joint, and the position
of the head relative to the ground
• Muscle spindles monitor the length of a
muscle during contraction
Body Position
• Your brain keeps track of movements and
combines these with information from the
middle ear to determine the position of the
body and it’s various parts in space